Help?

So here's the story:I was on here, and then somebody called, I didn't know who it was, so I didn't answer. Now they've called 9 times in the past 15-20 minutes. And just a second ago, someone was calling, and then another number that I didn't know started calling at the same time. When I was finally about to answer it, the calling stopped all of a sudden and it said, "ANSWERING". Then the ringing stopped. I'm kinda creeped out ATM, do you suggest anything to do?

That happens literally everyday to me. It's this group of people who call from various areas and it's an automated messaged, like, "Do you feel like you need a new car? New car insurance? Then stop by ______!" We just let it ring and don't pick it up. u_u